A burner of this type comprises a mixture nozzle, and a gas supply nozzle surrounding this mixture nozzle.
In a pulverized coal burner disclosed in JP-A-63-87508, an impeller for swirling an air-fuel mixture is provided within a mixture nozzle. The swirled mixture from an outlet of the mixture nozzle is rapidly diffused within a furnace, and is mixed with secondary air and tertiary air, supplied from a gas supply nozzle, in the vicinity of the outlet of the mixture nozzle. Therefore, a reduction area is not sufficiently formed, and a flame does not spread in the furnace. As a result, a part of fine pulverized coal remains unburned, and the production of NOx can not be suppressed.
In a pulverized coal burner disclosed in JP-A-60-200008, a throat portion is provided within a mixture nozzle, and an outlet of the mixture nozzle is flared. In this burner, as in the above-mentioned burner, an air-fuel mixture from an outlet of the mixture nozzle is rapidly diffused within a furnace, and is mixed with secondary air and tertiary air, supplied from a gas supply nozzle, in the vicinity of the outlet of the mixture nozzle. As a result, a part of fine pulverized coal remains unburned, and the production of NOx can not be suppressed.